1. Field of the Invention
This invention is concerned with the breaking or resolution of oil-in-water (O/W) bituminous emulsions by treatment with polyureas.
2. Description of the Prior Art
A great volume of hydrocarbons exist in known deposits of tar sands. These deposits occur at various places, the Athabasca tar sands in Canada being an example. The petroleum in a tar sand deposit is an asphaltic bitumen of a highly viscous nature ranging from a liquid to a semisolid. These bituminous hydrocarbons are usually characterized by being very viscous or even non-flowable under reservoir conditions by the application of driving fluid pressure.
Where surface mining is not feasible, the bitumen must be recovered by rendering the tar material mobile in-situ and producing it through a well penetrating the tar sand deposit. These in-situ methods of recovery include thermal, both steam and in-situ combustion and solvent techniques. Where steam or hot water methods are used, a problem results which aggravates the recovery of the bitumen. The difficulty encountered is emulsions produced by the in-situ operations. These emulsions are highly stable O/W emulsions which are made even more stable by the usual presence of clays. Most liquid petroleum emulsions are water-in-oil (W/O) types. These normal W/O emulsions are broken by methods known in the art. However, the bitumen emulsions which are O/W types present a much different problem, and the same demulsifiers used in W/O emulsions will not resolve the O/W bitumen emulsions. The uniqueness of these O/W bitumen emulsions is described in C. W. W. Gewers, J. Canad. Petrol. Tech., 7(2), 85-90 (1968). (Prior art Reference A.) There is much prior art concerning the resolution of normal W/O emulsions. Some of the art even mistakenly equates bitumen O/W emulsions with these W/O emulsions. The following is a list of several art references.
B. British Pat. No. 1,213,392 discloses a polyurethane for breaking W/O emulsions.
C. British Pat. No. 1,112,908 discloses the use of polyurethanes to break W/O emulsions. Even in a discussion of prior art, this British Patent discusses hydrophilic polyurethanes and indicates that they are ineffective for breaking emulsions.
D. U.S. Pat. No. 3,594,393 is also concerned with breaking W/O emulsions with polyurethanes.
E. U.S. Pat. No. 3,640,894 discloses polyurethanes and polyurethanes used in combination with Novolak alkoxylates to break W/O emulsions.
F. U.S. application Ser. No. 152,453 filed May 22, 1980, now allowed, claims a process for recovering petroleum from bitumen emulsions by demulsifying the emulsions with the reaction product of a polyisocyanate and diols and triols wherein the resulting polyurethane is greater than about 8,000 molecular weight.
It is an object of the present invention to provide a method whereby O/W bitumen emulsions may be broken by treatment with a class of polyureas.